Refactor Sätteri plugin support: replace mdast plugin with hast plugin for #end-of-markdown insertion

Author: martrapp

.changeset/afraid-toes-fetch.md

@@ -0,0 +1,7 @@
+---
+'astro-vtbot': minor
+---
+
+Fixes support for insertion of the #end-of-markdown id for Sätteri builds.
+
+Contrary to my previous assumption, the structure of Sätteri `mdast` plugins differs much from that of `remark` plugins. So I had to replace the `mdast` plugin with a `hast` plugin. See the [ documentation](https://events-3bg.pages.dev/library/StarlightPlugin/#for-sätteri-starlight-041) on how to use it.

README.md

@@ -13,15 +13,19 @@ The bag of tricks provides extensions & support around Astro's view transitions.
 
 A current deployment of tech demos and the documentation can be found at https://events-3bg.pages.dev/
 
-**Do not be put off by the major version bump!** The bump is a SemVer formality, but the chances of encountering the breaking change are very low. See below.
 
 ## !!! NEW TRICKS ✨ IN THE BAG 👜 !!!
 
-> If you use the Starlight with Sätteri, you can use `remarkEndOfMarkdown` [as an mdastPlugin](https://events-3bg.pages.dev/library/StarlightPlugin/#for-s%C3%A4tteri-starlight-041). If you prefer a more _mdasty_ name for the plugin: it is now also exported as `mdastEndOfMarkdown`.   
+> I had to rework the insertion of the `#end-of-markdown` marker used by the automatic `<link rel="expect" ...>` insertion for Sätteri. 
+> 
+> I'm sorry that the `mdast` approach did not work. `mdastEndOfMarkdown` isn't supported any more. If you tripped over this, hit me up on Astro's discord.
+>
+> If you run Starlight with Sätteri, you now have to use `hastMarkEndOfMarkdown` [as a hastPlugin](https://events-3bg.pages.dev/library/StarlightPlugin/#for-s%C3%A4tteri-starlight-041). 
+   
 
 ## Recently Learned Tricks ##
 
-> This release adds compatibility with Astro v7 while maintaining compatibility with earlier versions of Astro. The only breaking change is the removal of the `CreateAnimationScope.astro` component, which was never officially documented and was rarely, if ever, used. If you were using it, please get in touch on Discord (@martrapp) or Bluesky (@martr.app) and we will find a solution.
+> The 3.0.0 release adds compatibility with Astro v7 while maintaining compatibility with earlier versions of Astro. The only breaking change is the removal of the `CreateAnimationScope.astro` component, which was never officially documented and was rarely, if ever, used. If you were using it, please get in touch on Discord (@martrapp) or Bluesky (@martr.app) and we will find a solution.
 
 
 > Updated dependencies. Especially bumps @vtbag/utensil-drawer to current 1.2.13, where the `declarative-names` script now supports a special `:in-viewport` pseudo-class and `mayStartViewTransition()` supports scoped view transitions, if the browser does. For details see https://vtbag.dev/tools/utensil-drawer/

integration/starlight-view-transitions.ts

@@ -1,4 +1,5 @@
 import type { HookParameters, StarlightPlugin } from '@astrojs/starlight/types';
+import { defineHastPlugin } from 'satteri';
 import { resolve } from 'node:path';
 import { fileURLToPath } from 'node:url';
 import vtbot from 'astro-vtbot';
@@ -45,7 +46,30 @@ export function remarkEndOfMarkdown(id = 'end-of-markdown') {
 	};
 }
 
-export const mdastEndOfMarkdown = remarkEndOfMarkdown;
+export function hastMarkEndOfMarkdown(id = 'end-of-markdown') {
+	const seen = new WeakSet();
+	return defineHastPlugin({
+		name: 'mark-end-of-markdown',
+		element: {
+			filter: ['p'],
+			visit(node, ctx) {
+				const parent = ctx.parent(node);
+				if (parent?.type === 'root') {
+					if (!seen.has(parent)) {
+						seen.add(parent);
+						process.env.vtbotEndOfContentId = id;
+						ctx.appendChild(parent, {
+							type: 'element',
+							tagName: 'a',
+							properties: { id },
+							children: [],
+						});
+					}
+				}
+			}
+		}
+	});
+}
 
 function set(property: string, value: any) {
 	if (value === undefined) delete process.env[property];